PROJECT SUMMARY The detection of temperature change by nerve receptors in human tissues is a life?preserving function which is highly evolutionarily selected. Platelets show a unique response to cold with cytoskeletal rearrangement and low?level receptor activation. Temperature?gated transient receptor potential channels (Thermo TRPs) are a family of ion channels activated by temperature. Transient Receptor Potential Melastatin 8 (TRPM8) also known as Cold and Menthol Receptor 1 (CMR1), is a nonselective cation channel gated by cold?stimuli and various cooling reagents including menthol, eucalyptol, and icilin. In preliminary studies, we show that platelets express TRPM8, and the addition of TRPM8 agonists mimic typical morphologic and functional changes of platelets exposed to cold. The overarching goal of these studies is to characterize the molecular pathways through which platelets react to temperature changes. Further elucidating these mechanisms could lead to improved platelet storage conditions at 4C for transfusions, safer antiplatelet therapy, better prevention of heart attacks, and fewer side effects when therapeutic lowering of the body temperature after cardiac arrest is required. In aim 1 of this proposal, we will characterize the role of TRPM8 in platelets and elucidate its specific function for the cold platelet phenotype. This aim proposes to expand on our preliminary data that identified TRPM8 on human platelets and underscore its functional relevance. In aim 2 we will evaluate TRPM8 as a target for inhibition during platelet storage at 4C utilizing a small molecule TRPM8 inhibitor. In aim 3 of this proposal, we will determine the role of TRPM8 inhibition during 4C storage for recovery, survival, and function after transfusion in healthy human subjects.